Progress in proton radiography for diagnosis of ICF-relevant plasmas

Abstract

Proton radiography using laser-driven sources has been developed as a diagnostic since the beginning of the decade, and applied successfully to a range of experimental situations. Multi-MeV protons driven from thin foils via the Target Normal Sheath Acceleration mechanism, offer, under optimal conditions, the possibility of probing laser-plasma interactions, and detecting electric and magnetic fields as well as plasma density gradients with ps temporal resolution and 5-10 mm spatial resolution. In view of these advantages, the use of proton radiography as a diagnostic in experiments of relevance to Inertial Confinement Fusion is currently considered in the main fusion laboratories. This paper will discuss recent advances in the application of laser-driven radiography to experiments of relevance to Inertial Confinement Fusion. In particular we will discuss radiography of hohlraum and gasbag targets following the interaction of intense ns pulses. These experiments were carried out at the HELEN laser facility at AWE (UK), and proved the suitability of this diagnostic for studying, with unprecedented detail, laser-plasma interaction mechanisms of high relevance to Inertial Confinement Fusion. Non-linear solitary structures of relevance to space physics, namely phase space electron holes, have also been highlighted by the measurements. These measurements are discussed and compared to existing models.

Modeling of Intense Laser Driven High Energy Density Plasmas

“…In this pursuit the proton radiography diagnostic technique [76,22,15,156,23] has enjoyed considerable success, providing insight into megagauss-scale electromagnetic fields in inertial confinement fusion (ICF) implosions [132,119,111,82,186,114,118,68,21,190,115,137,139,138,117,224] , large-scale self-organizing electromagnetic field structures in high velocity counter-streaming plasma flows [97], magnetic reconnection processes [151,113,217], HED plasma instabilities [112,77,56,61,60] and more. Fig.…”

“…A key challenge stems from the fact that the radiographic image is not a one-to-one electromagnetic field map, but rather forms a convolution of the three dimensional fields with the sampling proton properties. Useful aspects of the field geometry have been deduced from qualitative inspection [135,16,17,18,156,23,125,217,21,70,32] , and by means of quantitative estimates based on scalings of the Lorentz force [79] when features of the plasma are known. [151,113,120,186,161,189,115,116,217,218,197,224] Recently analytic theory describing the deconvolution has been developed [98], but its application is constrained to simple field geometries and low field strengths, since the general mapping is nonlinear and degenerate.…”

Effective laser driven proton acceleration from near critical density hydrogen plasma

“…The fast recent progress has hinted that the extreme parameters of extreme light infrastructure will allow the production of ultra-high-energy ions (GeV and beyond) which will open the door to future unique applications like time and space resolved radiography of dense matter (Borghesi et al, 2010), injectors study for medical applications (Muramatsu and Kitagawa, 2012) for ion beam physics (Hoffmann et al, 2005).…”

Multispecies plasma expansion into vacuum: The role of secondary ions and suprathermal electrons

“…In high-power laser-plasma interaction experiments, on the other hand, qualitative evidence based on proton diagnostics [49] suggests that the electron population is not thermalized, while various types of non-Maxwellian situations, e.g. "bump-on-tail" distributions may develop, depending on the surrounding plasma environment.…”